The Greek verb egkaiein literally meant ‘to burn in’, being a compound of en-, ‘in’, and kaiein,‘to burn’. In fact the term denoted a particular method of painting which was practised by the ancients. According to a first-century account in the writings of Pliny the Elder, the process involved mixing pigments with hot beeswax, brushing them on to plaster and then smoothing and fixing them to the surface with a hot iron. (English derived the word encaustic from Greek in the seventeenth century to describe this kind of painting.) Whenever Greek or Roman emperors had documents of state to sign, they used an ink of imperial purple. The word for this special ink was egkauston, a derivative of the verb egkaiein.
By the time the term arrived in Old French as enque in the eleventh century by way of Late Latin encaustum , it simply denoted ordinary ink. Middle English took the term from Old French as enke in the mid-thirteenth century. Over the centuries ink has been applied to various substances used for writing or painting, including the strange viscous paste prepared by Mr Biro for his eponymous pens.